In what amounts to a kind of holiday gift to the cosmos, astronomers from NASA's Kepler spacecraft announced Tuesday that they had discovered a pair of planets the size of Earth orbiting a distant star. The new planets, one about as big as Earth and the other slightly smaller than Venus, are the smallest planets yet found beyond the solar system.
Astronomers said the discovery showed that the Kepler telescope, which was launched in 2009, could find planets as small as our own and was an encouraging sign that planet hunters would someday succeed in the goal of finding Earth-like abodes in the heavens.
In the past 15 years, astronomers have been chipping away at the sky, finding smaller and smaller planets. "We are finally there," said David Charbonneau, an astronomer at the Harvard-Smithsonian Center for Astrophysics, who was a member of the team that made the observations, led by colleague Francois Fressin.
The team reported its results in an online news conference Tuesday and in a paper being published in the journal Nature.
"This demonstrates for the first time that Earth-sized planets exist around other stars and that we can detect them," Fressin said.
The announcement doubled the number of known Earth-sized planets in the galaxy to four from two — Earth and Venus.
The next major goal in the planetary hunt, astronomers say, is to find an Earth-sized planet in the so-called Goldilocks zone of a star, where conditions are temperate for water and thus life.
The two new planets are far outside the zone and are too hot to contain life as we know it. Their star, which is slightly smaller and cooler than the sun, is about 950 light years away from us.